Air pressure indicator switch



March 26, 1940. o. c. SPURLOCK AIR PRESSURE INDICATOR SWITCH Filed June26, 1939 a Sheets-Sheet 1 ATTORNEYS March 26, 1940. o. c. SPURLOCK AIRPRESSURE INDICATOR SWITCH Filed Jxine26, 1939 s Sheets-Sheet 2 01/2 62"4 Spa/152g? ATTORNEYS March 26, 1940. Q SPURLQCK 2,195,155

AIR PRESSURE INDICATOR SWITCH Filed June 26, 1939 5 Sheets-Sheet 5 0/17flSpar/am INVENTOR ATTORNEYS Patented Mar. 26, 1940 UNITED STATES PATENTOFFICE AIR. PRESSURE INDICATOR SWITCH Oliver 0. Spurlock, Burrton, Kans.

Application June 26, 1939, Serial No. 281,279 3 Claims. (01. 20058) Thisinvention relates to air pressure indicators for pneumatic tires and hasfor an object to provide a simplified circuit closer adapted to beapplied to the vehicle wheel and actuated by predetermined low pressurein the inner tube to energize a signal circuit and warn the driver thatthe tire needs additional air.

A further object is to provide simplified electrical connections betweenthe circuit closer and an annular rotary contact ring carried by thebrake drum so that danger of short circuits will be reduced to aminimum.

A further object is to provide simplified brush mechanism carried by thestationary flange of the drum with which the contact ring has wipingengagement to assure good electrical con nections throughout therelatively movable parts of the signal circuits.

A further object is to provide apparatus of this character which will beformed of a few strong simple and durable parts which will beinexpensive to manufacture and which will not easily get out of order.

With the above and other objects in view the -33 invention consists ofcertain novel details of construction and combinations of partshereinafter fully described and claimed, it being understood thatvarious modifications may be resorted to within the scope of theappended claims with- 30 out departing from the spirit or sacrificingany of the advantages of the invention.

In the accompanying drawings forming part of this specification,

Figure 1 is a cross sectional View through a 5 vehicle wheel andpneumatic tire equipped with an air pressure indicator constructed inaccordance with the invention. 7

Figure 2 is a fragmentary side elevation of the wheel and parts of theinvention shown in Figure 1.

Figure 3 is a fragmentary longitudinal sectional view taken on the line33 of Figure 1.

Figure 4 is adetail cross sectional view taken on the line 4--4 ofFigure 2, drawn to enlarged 45 scale.

Figure 5 is a detail cross sectional view taken on the line 5-5 ofFigure 2.

Figure 6 is a detail cross sectional view taken on the line 66 of Figure2.

Figure '7 is a detail cross sectional view showing the brush andconductor ring.

Figure 8 is a diagrammatic view showing the electrical connections ofthe circuit closers on the wheels and respective pilot lamps.

Figure 9 is a detail cross sectional view of another form of theinvention in which the circuit closer is disposed on the side of the rimrather than on the inner periphery of the rim.

Figure 10 is a fragmentary bottom plan view of the parts shown in Figure9.

Figure 11 is a top plan View of the circuit closer shown in Figure 9.

Figure 12 is a cross sectional view taken on the line l2l2 of Figure 11.

Figure 13 is a cross sectional view taken on the line l3--l3 of Figure12.

Figure 14 is a cross sectional view taken on '16 lin l4l4 of Figure 13.

Referring now to the drawings in which like characters of referencedesignate similar parts in the various views, 10 designates a tire rim,H a tire equipped with an inner tube l2, l3 a brake drum, I4 thestationary back plate of the drum, IS the hub, IS the axle, and'i'l theaxle housing of conventional automotive vehicle wheel construction.

In carrying out the invention, a circuit closer is mounted on each wheeland comprises a casing l8, best shown in Figure 3, having attaching tabsl 9 at the bottom of the end walls through which screws 20 are passed tosecure the casing to the inner periphery of the rim I0 as best shown inFigure l. A plunger 2| is mounted radially in the casing and projectsthrough an opening 22 in the rim to engage the inner tube l2. Theplunger is threaded to receive a nut 24 and a helical spring 25 issleeved on the plunger beyond the nut and bears against the end wall ofthe casing to yieldably hold the plunger in engagement with the innertube. Adjustment of the nut varies the tension of the spring so that theplunger will yield inwardly with the tube upon predetermined lowpressure condition in the tube.

A metal plate 26 is provided with an opening near one end to receive theplunger between the spring and the nut so that the plate moves as a unitwith the plunger. The plate is equipped with a contact point 21 in thenature of a screw which is threadedly engaged in an opening near thefree end of the plate and is provided with an adjusting nut 28.

A second contact point 29, in the nature of a screw, is engaged throughan insulating bushing 30 disposed in an opening in one side wall of thehousing and is held in position to be engaged by the contact point 27through the medium of nuts 3| which bear against opposite sides of thebushing.

For confining the plunger 2| and the plate 26 to rectilinear movement atubular guide 32 is fixed to the inner wall of the casing within thespri' g 25 and slidedly receives the adjacent end of the plunger. Aguide rib 33 is secured to the end wall above the insulating bushing 30and the plate is provided with a notch in the end edge to receive theguide rib.

A nut lock St, in a nature of an L-shaped blank of insulating material,is disposed on the screw 29 and contacts with one of the Wrench faces ofthe inner nut 35 to prevent the nut from turning and changing theadjustment of the screw.

A contact ring is fixed to the inner face of the brake drum l3concentric with the axle l6 as best shown in Figures 1 and 6. For thispurpose blocks 36 of insulating material are interposed between the ringand the drum and a screw 3! is advanced through the ring into one end ofeach block. A screw 38 is advanced through the drum and into the otherend of the block. An insulating bushing 39 is disposed around the screw38.

For electrically connecting the ring with the contact screw 29, a leafspring it is secured intermediate its ends to the outer face of theconventional disc ii which forms the spokes of the drop center rim wheelillustrated. For this purpose a screw '1 engaged through an opening inthe spring and threaded into the disc. A block of insulation 4-3 isinterposed between the the iso and is provided with integral bushingsand :5 which insulate the spring from the screw and from the disc. Aconductor w re id is secured to the leaf spring at one end and at theother end is secured to the screw 23 which forms a stationary contactpoint as previoi y described.

A screw M is engaged through the contact ring and extends through aninsulating bushing 48 w'hi projects through opening in the brase drum 3.The so ew abuts the end of the leaf spring =18 and holds the leaf springunder sl ght tension so that good electrical contact be tween screw theleaf spring is promoted.

The signal circuit is conducted from the rotating contact ring throughthe stationary back plate H of the brake drum through the medium of ahollow tube est shown in Figures 1 and 7. tube exteriorly threaded andis enga ged through threaded opening Ei l formed in an insulated, plate'55 which is secured to the back plate i i of the brake drum through themedium of insulated screws 52. A lock washer E2 is t onto the tube andbears against the insulated E-l to hold the tube against dislodgement.The tube projects through an enlarged opening 54 formed in the backplate, and extends toward the contact ring 35. A plunger 55 is disposedin one end of the tube and the contact ring has wiping engagement withthe plunger. The plunger is yieldably held at its outer lii of movementthrough the medium of helical 563 which is disposed in the bottom of thetube 49 and bears at its outer end against the head or" an adjustingscrew 51 which. is threaded through a cap 58 on the outer end of thetube. The screw 5'! may be adjusted to regulate the tension or" thespring 55.

In order that the wheel may be put on the brake drum in only one way sothat the leaf spring will always register with the screw 47 and thuseliminate the possibility of disconnecting the wire a guide lug 59.shown best in Figure 5, is secured to the brake drum l3 and is adaptedto be received in a guide opening 65 formed in the flange of the disc 4!of the wheel.

As shown diagrammatically in Figure 8, each circuit closer is connectedby a conductor wire 6| to a respective pilot lamp 62 located withinconvenient reach of the driver of the vehicle. All the pilot lamps areconnected by a common conductor wire 63 to the battery 64. A switch 55is interposed in the conductor wire 63 for energizing the signalcircuits to test the tire pressure. When testing the tire pressure,should any tire be dangerously low, the contact points of the respectivecircuit closer will be in engagement with each other so that therespective pilot lamp will light. The diagram shows five wheels, but aswill be obvious, one of these wheels is the usual spare.

A modified form of the invention is shown in Figures 9 to 14 inclusive.In this form of the invention the only difference is in the location ofthe circuit closer on the side of the rim and the arrangement of thecontacts so that the latter will no be affected by centrifugal force.

In the modified form of the invention, 66 designates a housing shaped tofit snugly against the side of the drop center rim 61 and is providedwith mounting lugs 68 through which securing screws 69 are passed andthreaded into the side of the rim as shown in Figure 9. The housing isprovided with a removable cover 10 which is secured in place by screws Has shown in Figure 10.

By referring to Figures 13 and 14 it will be seen that the plunger 12 ismounted in the housing to extend laterally through the housing to engagethe inner tube 13 instead of extending radially through the housing andthus centrifugal force cannot interfere with the performance of theplunger. The plunger is mounted to slide in guides 14 formed on thehousing and is urged toward the tire by a helical spring 15 which issleeved on the plunger and bears against a con tact point support plate16 carried by the plunger as previously described.

A contact point 11 is adjustably mounted and is confined to rectilinearmovement through the medium of a guide rib 8 formed on the casing andengaged in a guide slot 19 formed in the end of the plate 76.

A second contact point 80 is mounted in the casing to extendperpendicular to the plunger 12 and is in the nature of a screw which isconfined in place through the medium of nuts 8|, best shown in Figure11, the inner not being held against dislodgement by a substantiallyL-shaped lock member 82 as previously described.

From the above description it is thought that the construction andoperation of the invention will be fully understood without furtherexplanation.

What is claimed is:

1. A circuit closer for mounting on the rim of a pneumatic tire,comprising a casing having attaching tabs, 2. plunger in the casingadapted to project through the rim and engage the inner tube of thetire, an adjus ing nut threaded on the plunger, a helical springesponsive to inner tube pressure between the nut and the casing, a metalplate secured at one end to the plunger between the spring and the nutto move as a unit udth the plunger, a contact point projecting at a.right angle from the plate, a second contact point car ried by andinsulated from the casing and adapted to be engaged by the first namedcontact point in circuit closing position, and guide means carried bythe casing for confining the plunger and the plate to rectilinearmovement toward and away from the inner tube.

2. The combination with a drop center rim and pneumatic tire thereon, ofa circuit closer comprising a casing secured to the side of the rim, aplunger in the casing extending laterally through the rim and engagingthe inner tube of the tire, an adjusting nut threaded on the plunger, ahelical spring responsive to inner tube pressure between the nut and thecasing, a metal plate secured at one end to the plunger between thespring and the nut to move as a unit with the plunger, a contact pointprojecting at a right angle from the plate, a second contact pointcarried by and insulated from the casing and adapted to be engaged bythe first named contact point in circuit closing position, and guidemeans carried by the casing for confining the plunger and the plate torectilinear movement toward and away from the inner tube.

unit with the plunger, a contact point projecting at a right angle fromthe plate, a second contact point carried by and insulated from thecasing and adapted to be engaged by the first named contact point incircuit closing position, a guide rib on the casing interfitting withthe free end of the plate, and a guide tube on the casing receiving theplunger, said rib and tube restricting the plunger and the plate torectilinear movement.

OLIVER C. SPURLOCK.

